<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
</head>
<body>
    <input class="btn" type="button" value="禁用文本框">
    <input type="text" class="inp">

</body>
<script>
    var btn = document.getElementsByClassName('btn')[0]
    var inp = document.getElementsByClassName('inp')[0]

    btn.addEventListener('click',function(){
       inp.disabled = inp.disabled === true? false : true;
       inp.style.background = 'yellow';
    })
</script>
</html>